Input inrush current control is often required, e.g., for AC/DC power supplies with bulk capacitors on the rectifier output to prevent a fuse or an upstream over current protection device from being triggered. Additionally, a hot pluggable telecom DC/DC power supply, e.g., a 48V DC/DC brick power supply, also needs an input inrush control circuit to protect the input pins from being damaged by arcing.
Conventional inrush control circuits are often implemented by a resistor in parallel with a relay. However, the relay control winding typically consumes 10 to 20 mA, which is more power consuming than desired, especially where the desire is to meet ENERGY STAR standby power requirements or other efficiency standards.
Alternative active inrush current control circuits may use a TRIAC in parallel with a resistor. While such alternative circuits do not have the same power loss issues as conventional inrush control circuits that include a relay, they need a floating bias gate drive source, which is not always practical and/or desired.
As can be appreciated from the above description, there is still a need for improved inrush current control circuits.